The Merkava series of main battle tanks are used by the Israel Defense Forces. The name comes from Hebrew: "chariot". The tank began development in 1973 and entered official service in 1978. Four main variants of the tank have been deployed. It was first used extensively in the 1982 Lebanon War. The name "Merkava" was derived from the IDF's initial development program name.
The Mark I, operational since 1978, is the original design created as a result of Israel Tal's decision, and was fabricated and designed for mass production. The Mark I weighed 63 tonnes and had a 900 horsepower (670 kW) diesel engine, with a power-to-weight ratio of 14 hp/ton. It was armed with the 105 millimeter M68 main gun (a licensed copy of the British Royal Ordnance L7), two 7.62 mm machine guns for anti-infantry defense, and a 60 mm mortar mounted externally, with its operator not completely protected by the tank's hull.
The Mark II was first introduced into general service in April 1983. While fundamentally the same as the Merkava Mark I, it incorporated numerous small adjustments as a result of the previous year's incursion into Lebanon. The new tank was optimized for urban warfare and low intensity conflicts, with a weight and engine no greater than the Mark I
The Merkava Mark III was introduced in December 1989 and was in production until 2003. As of 2016, the Merkava III is by far the most numerous tank in frontline IDF service. Compared to the Merkava II, it has upgrades to the drivetrain, powertrain, armament, and electronic systems. The most prominent addition was the incorporation of the locally developed IMI 120 mm gun. This gun and a larger 1,200 horsepower (890 kW) diesel engine increased the total weight of the tank to 65 tonnes (143,000 lb), but the larger engine increased the maximum cruising speed to 60 km/h (37 mph)
The Mark IV is the most recent variant of the Merkava tank that has been in development since 1999 and production since 2004. The upgrade's development was announced in an October 1999 edition of the Bamachaneh ("At the Camp") military publication. However, the Merkava Mark III remained in production until 2003. The first Merkava IVs were in production in limited numbers by the end of 2004.